Free-draining granular base for prepared ground surface

ABSTRACT

A prepared ground surface e.g. a pavement or roadway is provided with a free-draining aggregate layer between it and subsoil, there being positioned above and beneath the aggregate layer a water impervious barrier to prevent water entering the aggregate from passing downwardly into the subsoil or upwardly into the pavement or road surface material. In one embodiment the angle of the bottom impervious layer is such that water flows through beneath the roadway surface. In another embodiment water from either side of the roadway or pavement surface can flow to a central or midpoint and is the means for draining away water tending to collect therein. In one form the means comprises an interceptor section or gully conducting water longitudinally to a point of discharge.

United States Patent Gagle et al.

[ FREE-DRAINING GRANULAR BASE FOR PREPARED GROUND SURFACE [75] Inventors: Duane W. Gagle; Homer L. Draper,

both of Bartlesville, Okla.

[73] Assignee: Phillips Petroleum Company,

Bartlesville, Okla.

221 Filed: Apr. 22, 1974 211 App]. No.: 462,875

[52] US. Cl 404/28; 404/31 [51] Int. CL E01C 3/00 [58] Field of Search 404/27, 28, 31; 61/10, 61/1 1 [56] References Cited UNITED STATES PATENTS 2,044,498 /l936 Pearce 404/28 [451 Oct. 7, 1975 Primary Examiner-Mervin Stein Assistant ExaminerSteven Hawkins [5 7] ABSTRACT A prepared ground surface e.g. a pavement or roadway is provided with a free-draining aggregate layer between it and subsoil, there being positioned above and beneath the aggregate layer a water impervious barrier to prevent water entering the aggregate from passing downwardly into the subsoil or upwardly into the pavement or road surface material. In one embodiment the angle of the bottom impervious layer is such that water flows through beneath the roadway surface. In another embodiment water from either side of the roadway or pavement surface can flow to a central or midpoint and is the means for draining away water tending to collect therein. In one form the means comprises an interceptor section or gully conducting water longitudinally to a point of discharge.

5 Claims, 2 Drawing Figures US. Patent Oct. 7,1975 3,910,710

FREE-DRAINING GRANULAR BASE FOR PREPARED GROUND SURFACE This invention relates to the construction of a, freedraining granular or aggregate base for a prepared ground surface, e.g., a pavement or roadway. In one of its aspects the invention relates to a prepared surface upon a free-draining aggregate base.

In one of its concepts the invention provides a surface construction suitable for roadway, driveway, playground or parking lot the construction comprising a prepared surface upon a layer of aggregate and a water impervious barrier on top and below said aggregate whereby water finding its way into the aggregate as from the side of the prepared surface cannot drain down through the aggregate into the subsoil or work its way upwardly into the prepared surface. In another of its concepts the invention provides such a prepared surface, e.g., a roadway or pavement surface of asphalt cement layer (hot mix) supported upon an aggregate base laid upon the subsoil there being interpositioned between the subsoil and the aggregate base and the aggregate base and the asphalt surface a water impervious layer, the edges of the aggregate being open to receive and/or to discharge water which may reach the edges of the structure. In another of its concepts the subsoil and therefor the bottom surface of the aggregate is inclined from the edge or edges of the prepared surface or construction so that water received into the aggregate will drain through a focal point or place from which it can be drained away by suitable means, as further described herein.

ln light load or traffic road construction, driveways or parking or playground lots, it is customary to compact the subsoil, cover it with 5-8 inches of rolled granular base and then apply 2-3 inches of an asphalt cement layer (hot mix). A basic weakness of this type of construction is the inability of the granular base to retain its structural strength because water intrusion washes out the fines portion of the aggregate. Further, if the compacted subgrade is clay or contains a major fraction of clay, the aggregate often sinks into the clay when it has been softened by water. The softened aggregate/clay subbase cannot support traffic passing over the thin asphalt cement layer and large sink holes and chug holes develop.

The deleterious action of intruding water and the submersion of the aggregate layer into the water softened subsoil is prevented by the creation of a barrier between the subsoil and the aggregate layer and between the asphalt cement traffic course and the aggregate layer, respectively.

We have conceived a structure which will permit intruding water to pass, in effect, through the prepared surface, pavement or roadway, etc., all the while preventing the water from passing downwardly into the subsoil or upwardly into the prepared surface. Thus the subsoil will not be subject to softening due to the water intrusion, nor to having due to freezing and thawing. Similarly, the water will not pass upwardly into the asphalt or other surface and there do damage likewise. The water impervious barrier now preferred essentially consists of a polyolefin fabric such as Petromat fabric. Petromat fabric is a non-woven fabric of polypropylene fibers and is available from Phillips Petroleum Company, Bartlesville, Oklahoma. Petromat fabric is available in rolls of up to about feet width and lengths of up to about 300 lineal feet. Petromat fabric was a weight of about 4 to 6 ounces per square yard, a tensile strength in the warp direction of -90 pounds and a tensile strength in the fill or woof direction of about -100 pounds. Petromat fabric has been found to be superior to such materials as burlap mats, cotton fibers, woven cloth, etc., in this capacity for retention of asphaltic material.

A Trademark of Phillips Petroleum Company Any sealant mixture of material which will render the fabric impervious can be used. Now preferred is an asphalt-asbestos mixture as described in copending application Ser. No. 207,800 filed Dec. 14, 1971, Clarence R. Bresson, et al. In said application for a patent there is described and claimed an impervious cover structure coated with a mixture containing asphalt and asbestos fibers. The asphalt and asbestos fibers coating mixture can be used upon a polyolefin fabric such as a polyproplene fabric here described.

The asphalt-asbestos mixture which is applied is usually applied as a cut-back asphalt. The cut-back asphalt is prepared from an air-blown asphaltic material having a penetration of about 20-50, preferably 25-35, a minimum ductility at 77F of 5, and a Ring and Ball softening temperature of l60l75F.

The cut-back solvent used to prepare the cut-back asphalt is selected from kerosene, cycle oil, Stoddard solvent or, in general a hydrocarbon based material having an initial boiling point in the range of 160-450F, preferably 200-300F.

Sufficient cut-back solvent is used to make the resultant blend applicable to the surface by hot application not exceeding about 250F., i.e., at a temperature which will not exceed the melting point of polypropylene and thus adversely affect the fabric or the asphalt may be applied by spraying or brushing techniques at ambient temperatures. Usually about 20-100 parts by weight of solvent, preferably about 40-70 parts by weight per parts by weight of asphaltic 'material, are used.

The asbestos fiber is added to the cut-back asphalt in amounts from about 4-l5 parts/100 parts by weight of cut-back asphalt. It can have a fiber length of about 0.0l0.l in., preferably about 0.03-0.06 in. While the presence of longer fibers can be tolerated, the preferred range is more readily handled by the usual equipment and best improves the desirable properties of the asphalt, such as the penetration values.

It has been found that using an approximately 4 oz- /yd fabric, a cut-back asphalt with an asbestos fiber content of about 6-8, or more, parts by weight/100 parts by weight of cut-back asphalt is preferred, while for a 5 oz. web an asbestos fiber content of about 5-6 parts by weight/100 parts by weight in the cut-back asphalt is sufficient. About 0.25 to 2 gallons of such cutback asphalt sealant per square yard is applied to the surface and fabric.

It is within the scope of this invention to utilize, in addition to the now preferred asbestos containing cutback asphalt, a cut-back asphalt without asbestos fibers or alternatively, a cationic or anionic asphalt emulsion generally available from commercial sources, provided, however that sufficient asphalt be deposited in the fabric to render same substantially impervious to water. A suitable cationic emulsion, for example, is described in U.S. Pat. No. 3,625,119 (Gayle et al.) (Dec. 7, 1971) the disclosure of which is included herein by reference.

bearing surface and a subsoil underlying said surface, said surface and said subsoil having positioned therebetween a free-draining layer of aggregate capable of receiving some surface water, said layer of aggregate and said subsoil having therebetween a water-impervious barrier positioned such that water in the subsoil cannot pass upward into the aggregate and such that water in the aggregate drains away from both edges of the traftic-bearing surface toward some low point under said surface and passes through a drainage means which dis charges the water to some point away from the subsoil underlying the aggregate.

2. A structure according to claim 1 wherein the aggregate layer is open for water flow on both sides of the edges of the traffic-bearing surface.

3. A structure according to claim 2 wherein there is a water-impervious barrier positioned between the traffie-bearing surface and the aggregate layer.

4. A traffic-bearing construction structure having improved drainage and stability comprising a trafficbcaring surface and a subsoil underlying said surface, said surface and said subsoil having positioned therebetween a free-draining layer of aggregate capable of receiving some surface water, said layer of aggregate and said subsoil having therebetween a water-impervious barrier positioned such that the water in the subsoil cannot pass upward into the aggregate and such that the water in the aggregate cannot pass into the subsoil but will accumulate on said barrier and run to a point of drainage which insures that the water will not flow downward into the subsoil underlying the aggregate, and said aggregate and said traffic-bearing surface having positioned therebetween another water-impervious barrier.

5. A traffic-bearing construction structure having improved drainage and stability comprising a waterpermeable traffic-bearing surface and a subsoil underlying said surface, said surface and said subsoil having positioned therebetween a free-draining layer of aggregate capable of receiving some surface water, said layer of aggregate and said subsoil having therebetween a water-impervious barrier positioned such thta the water in the subsoil cannot pass upward into the aggregate and such that water in the aggregate cannot pass into the subsoil but will accumulate on said barrier and run to a low point where there is located a drainage means which discharges the water which accumulates on the water-impervious barrier to some point away from the subsoil underlying the aggregate, said waterimpervious barrier being extended upward to the edges of the traffic-bearing surface so that the only water which enters the aggregate is the water which has passed through the water-permeable traffic-bearing 

1. A traffic-bearing construction structure having improved drainage and stability comprising a traffic-bearing surface and a subsoil underlying said surface, said surface and said subsoil having positioned therebetween a free-draining layer of aggregate capable of receiving some surface water, said layer of aggregate and said subsoil having therebetween a water-impervious barrier positioned such that water in the subsoil cannot pass upward into the aggregate and such that water in the aggregate drains away from both edges of the traffic-bearing surface toward some low point under said surface and passes through a drainage means which discharges the water To some point away from the subsoil underlying the aggregate.
 2. A structure according to claim 1 wherein the aggregate layer is open for water flow on both sides of the edges of the traffic-bearing surface.
 3. A structure according to claim 2 wherein there is a water-impervious barrier positioned between the traffic-bearing surface and the aggregate layer.
 4. A traffic-bearing construction structure having improved drainage and stability comprising a traffic-bearing surface and a subsoil underlying said surface, said surface and said subsoil having positioned therebetween a free-draining layer of aggregate capable of receiving some surface water, said layer of aggregate and said subsoil having therebetween a water-impervious barrier positioned such that the water in the subsoil cannot pass upward into the aggregate and such that the water in the aggregate cannot pass into the subsoil but will accumulate on said barrier and run to a point of drainage which insures that the water will not flow downward into the subsoil underlying the aggregate, and said aggregate and said traffic-bearing surface having positioned therebetween another water-impervious barrier.
 5. A traffic-bearing construction structure having improved drainage and stability comprising a water-permeable traffic-bearing surface and a subsoil underlying said surface, said surface and said subsoil having positioned therebetween a free-draining layer of aggregate capable of receiving some surface water, said layer of aggregate and said subsoil having therebetween a water-impervious barrier positioned such thta the water in the subsoil cannot pass upward into the aggregate and such that water in the aggregate cannot pass into the subsoil but will accumulate on said barrier and run to a low point where there is located a drainage means which discharges the water which accumulates on the water-impervious barrier to some point away from the subsoil underlying the aggregate, said water-impervious barrier being extended upward to the edges of the traffic-bearing surface so that the only water which enters the aggregate is the water which has passed through the water-permeable traffic-bearing surface. 